COOLmob Chats: Sandra Howlin on how tropical architecture can evolve to become more efficient

Left to right: Vicki Kerrigan, Robin Knox, Sandra Howlin, Nick Kirlew, Jo Rees and Ian Hollingsworth

COOLmob hosted a panel discussion as part of the Ripple Effect at the Nightcliff Seabreeze Festival. We chose to explore an extremely topical and relevant issue facing Darwin: Is Tropical Architecture Dead? The collision between sustainable housing design and energy efficiency. A panel of 5 local experts including Sandra Howlin, Robin Knox, Dr. Ian Hollingsworth, Nick Kirlew and Jo Rees came together to share their views.  

COOLmob followed up with Sandra Howlin, who argued that tropical architecture can evolve to become more energy efficient.  

COOLmob: Sandra, can you tell us a bit about yourself and your background?  

Sandra: I am passionate about energy efficient buildings and the reduction of CO2 emissions from our built environment. I currently lecture Building Design Drafting at CDU, in a previous role I was an accredited NatHERS energy rating assessor. I have performed hundreds of energy ratings using the NatHERS star ratings software on various house types including new elevated lightweight style houses, ground level blockwork houses, duplexes and high-rise apartments across the NT 

COOLmob: What are some features on homes in the NT housing stock that contribute to a higher rating?  

Sandra: The house types that preformed best & earned the highest star ratings were the houses that adopted good orientation, shade and natural ventilation via 100% openable windows, and encourage indoor/outdoor living and natural cross flow ventilation all great examples of the traditional tropical design features for passive cooling. But the houses that performed best had more than passive features alone, these houses had a dual function, a good balance, because they also performed well when air-conditioning was used, they were insulated and could be sealed, this dual functionality is key to energy efficient houses in our tropical climate.  

Extensive use of air-conditioning in our workplaces, hospitals and schools has seen the local population becoming more accustomed to a more comfortable indoor temperature, and this coupled with increasing temperatures and high humidity levels has increased the usage of air-conditioning in our homes, but we are still playing catch up when it comes to designing our homes for efficient air-conditioning use.  

COOLmob: Australia has a National Construction Code, which the NT is subject to, which provides the minimum necessary requirements for new buildings, including sustainability in the design, construction and performance. Why are the NT minimum standards lagging the rest of Australia? 

Sandra: Some basic minimum standards for energy efficiency in residential buildings were first introduced across Australia via the National Construction Code (NCC) in 2003. The NatHERS star energy ratings requirement is only one of the optional methods of compliance with the NCC for energy efficiency. It was first adopted by the NT in 2009, where all new houses and renovations to existing houses in the Northern Territory (NT) must achieve a 5-star energy rating and all new apartments built in the NT must achieve a 3.5-star energy rating. No minimum energy rating for other types of buildings has ever been adopted in the NT under the NCC. 

2009 was 10 years ago! For 10 years we have seen no increase in the minimum energy ratings requirements beyond 5-stars in the NT, what we have seen is a rise in energy consumption in our homes and in our power bills too.  

Other Australian states and Territories are advancing, the NCC 2019 release has seen a marked increase in the minimum NCC compliance requirements nationally to a 6-star minimum requirement, but in the NT these new more stringent regulations have not been adopted.  

Many new suburbs in Darwin already have houses with 6 star ratings as this is mandated not by the NCC, but by the suburbs own covenant agreements, newer suburbs such as Muirhead, in the Northern Suburbs and Bellamack in Palmerston have been insisting on 6 star ratings for new builds for many years, proving that it is not only possible but quiet easily achievable in this region.  

COOLmob: Ideally, how can we design home for efficient air-conditioning use? If we’re being realistic, whist COOLmob advocate for passive design and not relying on the A/C, as global warming continues, it is going to get hotter and harder to retain a comfort levels in the home.  

Sandra: The average household in Darwin already uses a mix of both passive means of cooling such as natural ventilation, shade, orientation and insulation and active means such as air/conditioning and fans to create an indoor environment that is comfortable to live in, our house and apartment designs must evolve to accommodate both passive and active means of cooling in an efficient manner. We are no longer in the 70’s and 80’s when dry seasons were cold, the day time temperature rarely rose above 30 degrees, back when air-conditioning was seen as a luxury. 

Recently I asked one of Darwin’s major house builders a question.  

How many of your clients who have approached you for a new home in the last 10 years gave you a brief that requested a non-conditioned home? His answer was NONE. ZERO. No one in the last ten years wanted to build a new home that could not accommodate air-conditioning. 

Many still hold an ideology that we can live comfortably without air-conditioning if our houses are designed for this climate, a stroll through our older suburbs of to view our traditional hot climate designs such as our elevated houses provides really good examples of large openable louvered windows to capture the breezes, wide overhangs to shade our glazing , good orientation and large lot sizes, they seemingly have it all in terms of good tropical design, but even these gems of good passive design cannot provide all of the human comfort the occupants require, the evidence of this is that you can also count at least four or five air-conditioning condensers hanging of the side of most traditional tropically designed houses. These older tropical elevated style houses are simply not designed to accommodate air-conditioning. And retro-fitting air-conditioning into leaky uninsulated traditional hot climate house simply converts these homes into the most inefficient residential type buildings in our city. 

We must move beyond the ideology that the way to keep our energy usage low is to avoid air-conditioning usage altogether, in hanging onto this ideology we are preventing the advancement of energy efficient homes that can and do use air-conditioning.  

So, in, 2019 let’s acknowledge that the majority of homes are provided with air-conditioning, let’s put the old argument that we can live without a/c to bed and instead concentrate on the next step advancing our typical building designs so that they perform well while they are being air-conditioned and have the ability to be passively cooled when the ambient outside conditions allow. By adopting this dual function approach, we can advance towards more energy efficient building design while incorporating the aesthetics and sound passive design principles of tropical architecture for the 21st century.  

COOLmob: And how do you see that we can we design for air-conditioning considerations, whilst still promote passive design principles? 

Sandra: Designing to accommodate air conditioning is not to say that we no longer adhere to the principles of tropical design and passive cooling good orientation, shade and crossflow ventilation, will continue to be crucial for all dwelling types regardless of their construction type, passive cooling reduces heat loads on the building, this ensures that the occupants stay cooler for longer and therefore do no reach for the a/c remote control quiet so quickly!  Insulation is critical for the building envelope, where the walls, roof and floors are insulated this further reduces the load on the air-conditioners meaning it does not have to work so hard!  It uses less energy, reducing both cost and consumption resulting in a more effective and efficient usage of power for cooling, while achieving good quality human comfort in our homes and reducing carbon emissions.   

It must be recognised that with increased air-conditioning usage, insulation levels must increase and sealing the building envelope to avoid air leakage is essential to hold the cooler conditioned air inside for longer, this a must in air-conditioned rooms to improve energy efficiency. We are Territorians, we know this! Because every time we want to keep our beer cold we use an esky and we close the lid in a hurry and when the seals are broken we get them fixed! And no, I am not saying we should live in houses that look like eskies, just houses that perform like eskies!  

COOLmob: Ok so insulation and seal ability is a must-have for home retrofitting for air-conditioning use or being built with air-conditioning as an optional cooling method? 

Sandra: Insulation works best when it is placed in our walls, roofs and floors in a continuous manner during construction, this is more difficult to achieve when retrofitting air-conditioning in spaces that have existing walls & roofs. However, there are options for seal ability that every house could retrofit, providing seals to both windows and external doors to avoid air leakage, upgrading older windows with modern, sealable glazed openings and retrofitting insulation in roof spaces are all costeffective methods of improving energy efficiency in existing air-conditioned buildings 

Most residents only consider the cost of the air-conditioner itself when retrofitting however air-conditioning poorly designed uninsulated, leaky home is a very inefficient use of air-conditioning and will result in higher power consumption and associated costs.   

A well-insulated and sealed home is ideal where a temperature different exists between inside and out, it is the most energy efficient way to use active energy.  No-one is suggesting that we should live in a building that looks like an esky, just one that performs like one. Ideally, a blend of the aesthetics of tropical design, the passive cooling principles of tropical design, large openable areas of high performance glazing with 100% openable area and the necessary efficient building envelope design and air-conditioning will emerge and evolve to form a new modern Tropical House style that suits the modern-day requirements of the occupants for human comfort in our city and across the NT.  

COOLmob: In 2017, a report was Published by The Dept. of the Environment and Energy, Application of NatHERS Software in Northern Australian Climates. Can you explain what this report found?  

Sandra: This report was commissioned specifically to investigate how the NatHERS star ratings software using the chenath engine models thermal comfort to produce the star ratings in tropical locations across Northern Australia. This report was in response to suggestions that the National Home Energy Rating Scheme (NatHERS) star rating does not appropriately value traditional hot climate house design principles in tropical and hot climates, if you have any doubts regarding how the software works in our tropical climate I encourage you to read this report in full.  

The main concern since the introduction of the NatHERS software modelling tools is that the star ratings do not satisfactorily reward the comfort benefits of cross ventilation from opening windows. Instead, it has been suggested for some time that NatHERS software rewards a ‘sealed box’ design i.e. smaller windows and heavily insulated, and therefore reinforces inappropriate dwelling design in hot climates.  

The report provides evidence that  

  • that NatHERS software makes extensive use of natural ventilation to provide comfort 
  • the software does provide significant reward for traditional hot climate design techniques, such as shade, good orientation and natural ventilation.  
  • The model opens windows far more frequently to provide comfort than air conditioning in all climates and for all types of house designs 
  • Significantly higher star ratings that can be obtained using traditional designs  

The report goes further to assess why the majority of new houses we see being built in Darwin are ground level block work homes?  

The answer: because it is cheaper to comply with current 5 star requirements by building as ground level block work home.  

The report advises that if higher star ratings levels were adopted, more widespread adoption of traditional hot climate design strategies would be taken up by the market and concludes that it is because traditional design strategies are more expensive that the low heat gain approach of blockwork combined with smaller openings is more frequently used.  

Over the last decade there have been many local objections to increasing the minimum star ratings required in the NT, there has been much discussion as to the benefits of these initiatives which are mandated through the NCC & the NatHERS star ratings in the NT, we have seen continued to delay setting higher standards by increasing from say 5 to 6 stars and beyond, while this discussion persists.  

Doubts in how the software works in the tropics has prevented the NT moving forward for too long, the revelations of the 2017 report should put fears to bed and that all house designers can move forward with confidence in the NatHERS thermal modelling and the NCC regulatory system. 

It’s time to stop hanging onto the past, it’s time to evolve and move forward and to except the challenge of designing buildings that suit modern day lifestyles, occupant expectations and expectable human comfort levels with optimum energy efficiency.  

Thank you Sandra for sharing your wisdom and helping raise awareness amongst our community around the importance of climate suitable homes.